Dresden 2017 – CPP
Friday
CPP 68: Hydrogels and Microgels II
Time: Friday 10:15–13:15
Location: ZEU 260
CPP 68.1
Fri 10:15
Thomas Hellweg1 — 1 Bielefeld University, Bielefeld, Germany —
2 Laboratoire Charles Coulomb, Université de Montpellier, Montpellier, France
ZEU 260
Modelling photothermal control of gold nanoparticle loaded
microgel systems — ∙Dmitry Chigrin1,2 , Gero von Plessen1 ,
Ahmed Mourran2 , and Martin Möller2,3 — 1 Institute of Physics
(1A), RWTH Aachen University, Aachen, Germany — 2 DWI - Leibniz Institute for Interactive Materials, and Functional Interactive Polymers, Aachen, Germany — 3 Institute of Technical and Macromolecular
Chemistry, RWTH Aachen University, Aachen, Germany
A gel is a dispersed system which consists of at least two different
components: a solid or flexible mesh and a fluid. If the fluid is water the gel is called a hydrogel. Microgels are gels smaller than 10
𝜇m and can be used in a wide range of applications like drug delivery
and smart surface coatings. If the microgel consists of acrylamides
like N-isopropylmethacrylamide (NIPMAM) or N-n-propylacrylamid
(NNPAM) as network component, they show a volume phase transition (VPT) at a certain temperature, the volume phase transition temperature (VPTT). An increase in temperature above the VPTT leads
to an abrupt decrease in size and a decrease in temperature leads to an
abrupt increase in size. The VPTT is specific for each monomer. To
use microgels in sensors or for nanoactuators the thermoresponse has
to be precise and well known. That is why we investigated microgels
with a complex architecture containing NIPMAM and NNPAM. These
particles show a tunable linear change in size between the two VPTTs
of NNPAM (22 ∘ C) and NIPMAM (43 ∘ C). Furthermore, we deposited
these microgels on surfaces and investigated the properties of the microgel coating. The properties of these particles (like phase transition
behavior or particle size) can be adjusted by selecting specific synthesis
conditions.
Temperature-responsive microgels can exhibit extremely large deformations due to the volume transition in response to changes in temperature. Combining photothermal materials, e.g. plasmonic nanoparticles, with microgels opens a unique opportunity to design microdynamical systems (microswimmers, microactuators, micromachines)
which can be controlled all-optically. In this presentation we discuss
physical modelling of gold nanoparticle loaded microgels. A description
of photothermally activated microgels involves self-consistent coupling
of diffusion, elasticity, heat transfer and electrodynamic models. Using simple examples we discuss how swelling/de-swelling dynamics of
microgels can be controlled and guided using light.
CPP 68.2
Fri 10:30
ZEU 260
Magneto-optical and magneto-rheological properties of a
physical hydrogel based on 12-hydroxystearic acid — Hajnalka Nádasi1 , Ralf Stannarius1 , Peter Salamon2 , Tamas
Börzsönyi2 , and ∙Alexey Eremin1 — 1 Institute of Experimental
Physics, Otto von Guericke University Magdeburg, Universitätsplatz 2,
39016 Magdeburg, Germany — 2 Wiegner Research Centre for Physics,
Institute for Solid State Physics and Optics, Budapest, H-1525, Hungary
CPP 68.5
We investigate magneto-responsive physical ferrogels based on 12hydroxystearic acid in dodecane, doped with commercial magnetic
nanoparticles APG 935. The gelator molecules form a hydrogen-based
gel network at room temperature. The pure gels exhibit extraordinary helical filament nanostructures similar to those of the HNF(B4)
liquid crystal phase formed by bent-core mesogens. The rheological behaviour of the ferrogel is found to be strongly dependent on the preparation protocol. The ferrogels prepared in a magnetic field exhibit
lower storage modulus, which can be attributed to rearrangements of
the magnetic particles embedded in the gel matrix. At higher shear
rates, a gel-sol transition occurs. In a magnetic field, the interaction
between the magnetic particles and the matrix lead to an increase of
both storage and loss moduli.
The authors acknowledge the support by DFG (SPP 1681, STA
425/36-2)
CPP 68.3
Fri 10:45
ZEU 260
CPP 68.6
Fri 11:30
ZEU 260
Uptake and stability of pH-Sensitive Gold Nanoparticles
(AuNPs) in Thermoresponsive Polymer Brushes — ∙Dikran
Kesal1 , Patrick Krause1 , Marcus Trapp2 , and Regine von
Klitzing1 — 1 TU Berlin, 10623 Berlin, Germany — 2 Helmholtz Zentrum Berlin, 14109 Berlin, Germany
We investigate the rheological property of microgel monolayers at the
water/oil interface using passive and active microrheological methods.
At low surface coverage, the microgels at the water/oil interface have
a tendency to form aggregated structures (networks) with dominating
elasticity. At high surface coverage the microgels form densely packed
monolayers. Using microsized magnetic particles as the local rheological probes in the dense microgel monolayers, we perform in situ study
of their rheolocial properties and structures. We observe four regimes
where the elasticity of the microgel monolayer has different dependence on the microgel concentration at the interface. The rheological
properties of the microgel monolayers are not only dependent on the
concentration, but also strongly correlated with the inter-microgel distance and spacial arrangement of the microgels at the interface. Our
results also show that the microgel monolayers act similar to soft glassy
materials.
Fri 11:00
ZEU 260
Stimuli-responsive polymer brushes are widely applicable, i.e. for
self-cleaning coatings, switchable adsorbers and sensors. Using controlled reaction schemes, e.g. ATRP (atom transfer radical polymerization), tailor-made ultrathin brushes can be synthesized. These
brushes respond reversibly to stimuli, e.g. temperature, pH, or
biomolecules within micro-/milliseconds. Hence, these brushes pose
a pathway to innovative miniaturized devices. Tailoring the brushes
towards bioapplications requires an insight on their inner structure
without and with biomolecules. Here, TOF-SIMS has been applied
to obtain three-dimensional molecular information from PDMAEMA
(Poly(N,N-dimethylaminoethyl methacrylate) brushes with nm depth
resolution. For varying initiator densities, the relative density of initiator prior and after the polymerization as well as the polymer chain
density has been obtained. Further, the distribution of BSA (bovine
serum albumin) has been examined. The TOF-SIMS experiments were
complemented by XPS, AFM and fluorescence spectroscopy measurements. The results reveal the inner structure of polymer brushes of
varying grafting densities without and with protein.
Structure and rheology of microgel monolayers at the water/oil interface — ∙Shilin Huang1 , Kornelia Gawlitza2 ,
Regine von Klitzing2 , Werner Steffen1 , and Günter K.
Auernhammer1 — 1 Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany — 2 Stranski-Laboratorium
für Physikalische und Theoretische Chemie, Technische Universität,
Berlin, Strasse des 17. Juni 124, 10623 Berlin, Germany
CPP 68.4
Fri 11:15
Analysis of PDMAEMA Polymer Brushes: A TOF-SIMS
Study — ∙Marc Thomas1,2 , Ulrich Hagemann2,3 , Steffen
Franzka2,3 , Mathias Ulbricht1,2 , and Nils Hartmann1,2,3 —
1 Chemistry Department, University of Duisburg-Essen, Germany —
2 Center for Nanointegration Duisburg-Essen (CENIDE), University of
Duisburg-Essen, Germany — 3 Interdisciplinary Center for Analytics
on the Nanoscale (ICAN), University of Duisburg-Essen, Germany
Polymer brushes are polymers tethered to a surface or interface by
one end, which at sufficiently high grafting densities show a stretched
conformation away from the surface. Many of its applications, for e.g.
sensoric and catalysis, involve interaction with particles of some kind,
so understanding the interactions between nanoparticles and polymer
brushes is of great importance. Embedding nanoparticles, e.g. AuNPs,
in polymer brushes result in nanocomposite materials with novel optical properties.
In this work, the assembly of charge switchable AuNPs inside neutral charged Poly(N-isopropylacrylamide) (PNIPAM) brushes will be
discussed. The 5 nm AuNPs are capped with mercaptopropionic acid
(MPA, pKa 5.5) which bears a carboxylate group and is either protonated (uncharged) or deprotonated (negatively charged) depending
on the pH. While some recent efforts have been made in terms of particle uptake and distribution in weakly (PDMAEMA) and strongly
ZEU 260
Linear thermoresponsive acrylamid based microgels adsorbed
on a surface — ∙Marian Cors1 , Julian Oberdisse2 , and
1
Dresden 2017 – CPP
Friday
(PMETAC) charged polymers due to electrostatic interaction between
particle and brush. While PNIPAM brushes are neutral charged and
can only interact via H-bonding with the AuNPs, here the focus is
on understanding how protonating and deprotonating of the AuNPs
affect particle loading, distribution and stability in PNIPAM brushes.
to macromolecules. Rotational dynamics of such spin labels on time
scales between 10 ps and 1 𝜇s can be characterized by basic and fast
CW EPR spectroscopy. The dynamics of the spin labels is influenced
by the restricted motion of the side group bearing the label and local
polymer backbone motions at the point of the covalent attachment of
the label. The dynamics of polyelectrolyte complexes (PECs) composed of poly(diallyldimethylammonium chloride) (PDADMAC) and
poly(acrylic acid) (PAA) was studied in dependence on pH and temperature using a spin-labeled PAA as reporter molecule. All of the
experimental spectra were well reproduced by simulations based on
the microscopic order/macroscopic disorder (MOMD) model. It was
found that the segmental mobility of the PAA in the PECs is nearly
constant in the range of pH from 10 to 5 but decreases dramatically
for pH values lower than 5. It has been confirmed that the dynamics
in the PECs is strongly influenced by the degree of dissociation of the
weak polyacid.
15 min break
CPP 68.7
Fri 12:00
ZEU 260
Surface forces of polyelectrolyte multilayers in different
growth regimes — ∙Heba S. Mohamad, Malte Paßvogel,
Annkatrin Sill, and Christiane A. Helm — Inst. of Physics, Greifswald University, D-17487 Greifswald
Interaction with the surface of polyelectrolyte multilayer films is important for many application. The films built from Poly (styrenesulfonate) (PSS) and poly (diallylmethylammonium) (PDADMA) in 0.1
Mol/L NaCl start with a parabolic growth regime. Then a transition to linear growth occurs. In the linear growth regime, there are
more positive PDADMA than negative PSS monomers in the film;
therefore Na1 ions are incorporated. PDADMA and PSS terminated
films in the parabolic growth regime show flat surfaces which interact
purely electrostatically, as surface forces measurements with the colloid
probe technique show. In the linear growth regime, PSS terminated
films are also flat, but PDADMA terminated films interact by steric
forces which are analysed with the Alexander-de-Gennes theory. The
PDADMA chains protruding into solution are attributed to the excess
PDADMA monomers within the film. We conclude that choosing the
growth regime allows to control the surface interactions.
CPP 68.8
Fri 12:15
CPP 68.10
ZEU 260
The exponential growth regime of polyelectrolyte multilayer films made
from binary polyanion mixtures is investigated. Films were assembled
by the layer-by-layer (LbL) technique using poly(stryrene sulfonate)
PSS as polyanion and poly (diallyldimethylammonium) (PDADMA)
as polycation and investigated with in-situ ellipsometry and neutron
reflectivity. The films grow exponentially if molecular weight Mw(PSS)
is below 25 kDa; no exponential film growth occurs if Mw(PSS) is above
this threshold. Exponential growth is characterized by diffusion of PSS
within the film; in non-exponential growth regimes PSS is immobile.
The influence of PSS molecular weight distribution on exponential film
growth is investigated using a PSS mixture with molecular weight below and above the threshold value. Multilayer films grow exponentially
if the mole fraction of non-diffusing PSS is less than 1 %. Neutron reflectivity shows that the mole fraction of non-diffusing PSS in the film
is much larger than in the preparation solution. The effect gets more
pronounced with increase of the adsorption time. This finding is attributed to the irreversible adsorption of immobile PSS which replaces
mobile PSS which adsorbed first.
Fri 12:30
ZEU 260
Recently, polyelectrolyte complex (PEC) particle coatings were shown
to release ionic bone therapeutic drugs in sustained manner immediately after contact to buffer solutions. To trigger thermally on
demand the drug release thermoresponsive PEC particle coatings
based on poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AA)
and cationic cellulose (EDAC) were fabricated. EDAC/PNIPAMAA dispersions featured hydrodynamic radii RH=260-860 nm for
T=25∘ C and RH=60-140 nm for T=50∘ C due to coil/globule transition (CGT) of PNIPAM moieties above lower critical solution temperature (LCST). Coatings of EDAC/PNIPAM-AA particles at germanium
model substrates kept adhesive after buffer rinsing. FTIR spectroscopy
at EDAC/PNIPAM-AA revealed significant hydrogen bonding state
changes and broad phase transitions as a function of temperature as
well as higher LCST values for dispersions (45∘ C) and coatings (50∘ C)
compared to PNIPAM solutions (33∘ C). EDAC/PNIPAM-AA coatings
were loaded with zoledronate (ZOL) and at T>LCST ZOL was released
faster compared to T<LCST. Presumably, CGT partly compacts and
defects the PEC phase enabling faster ZOL elution.
Composition of polyanion mixtures influence exponential
growth of polyelectrolyte multilayers — ∙Annkatrin Sill1 ,
Malte Paßvogel1 , Antonia Weltmeyer1 , Olaf Soltwedel2 ,
Amir Azinfar1 , Peter Nestler1 , and Chrstiane A. Helm1 —
1 Inst. of Physics, Greifswald University, Germany — 2 Physics Department, TU Munich, Germany
CPP 68.9
Fri 12:45
Drug delivery by thermoresponsive polyelectrolyte complex coatings for bone healing — ∙Martin Müller1,2 , David
Vehlow1,2 , and Birgit Urban1 — 1 Leibniz-Institut für Polymerforschung Dresden e.V., Abteilung Polyelektrolyte und Dispersionen, 01069 Dresden, Germany — 2 Technische Universität Dresden,
Fachrichtung Chemie und Lebensmittelchemie, 01062 Dresden, Germany
CPP 68.11
Fri 13:00
ZEU 260
Spontaneous jumping and long-lasting bouncing of solid Leidenfrost drops — ∙Doris Vollmer, Maxime Paven, Tadashi Kajiya, Hans-Jürgen Butt, and Jonathan Pham — MPI for Polymer
Research, Mainz
The impact and rebound of liquid drops on hot, solid surfaces is of practical importance in industrial processes, such as thermal coating and
spray cooling. The impact of solid spheres is also a commonly encountered event in ball milling, powder processing, and everyday activities,
such as ball sports. Liquid drop and solid ball impacts are distinct
from each other in terms of their mechanics. Here, we show that hydrogels display unique characteristics of both solids and liquids when
heated above the Leidenfrost temperature. Using high speed video microscopy, we demonstrate that millimetric hydrogel drops jump from
a hydrophilic surface upon heating and continue to bounce several
times with increasing height. While elasticity dominates the mechanics of contact, evaporation supports long-lasting bouncing. This interplay between elastic and liquid properties results in intriguing dynamics, which is reflected in spontaneous jumping, long-lasting bouncing,
trampolining, and the shortest contact times ever observed for waterlike systems.
ZEU 260
Segmental Dynamics of Spin-Labeled Poly(acrylic acid) in
Polyelectrolyte Complex Coacervates Studied by CW EPR
Spectroscopy — ∙Uwe Lappan, Brigitte Wiesner, and Ulrich
Scheler — Leibniz-Institut für Polymerforschung Dresden e.V., Hohe
Straße 6, 01069 Dresden, Germany
The complex coacervation of oppositely charged polyelectrolytes has
been studied by continuous wave (CW) EPR spectroscopy. The spinlabel technique employs stable radicals which are covalently attached
2